The ornamental design for a piston for an internalcombustion engine, as shown and described.
FIG. 1 shows a first side and bottom perspective view of a piston for an internal combustion engine, showing our new design, with the view rotated 180 degrees being identical;
FIG. 2 shows a second side and bottom perspective view thereof, rotated 45 degrees from FIG. 1, with the view rotated 180 degrees being identical;
FIG. 3 shows a bottom view thereof; and,
FIG. 4 shows a cross-sectional view thereof, along lines IV-IV of FIG. 3.
The areas shown in broken lines depict environmental structure only and form no part of the claimed design.